<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <meta http-equiv="X-UA-Compatible" content="ie=edge" />
    <title>行内元素/行内块元素水平居中对齐</title>
    <style>
      /* 行内元素或者行内块元素水平居中给其父元素添加 text-align:center 即可 */
      .header {
        width: 900px;
        height: 200px;
        background-color: pink;
        margin: 100px auto;
        text-align: center;
      }
    </style>
  </head>
  <body>
    <div class="header">
      <span>里面的文字</span>
    </div>
    <div class="header">
      <img src="images/down.jpg" alt="" />
    </div>
  </body>
</html>
